Reversing mechanism for type impression machines



Dec. 5,1961 G. SCHENK 3,011,434

REVERSING MECHANISM FOR TYPE IMPRESSION MACHINES Filed Dec. 12, 1960 INVENTOR.

GUSTAV SC-HENK United States Patent 3,011,434 REVERSING MECHANISM FOR TYPE IMPRESSION MACHINES Gustav Schenk, Zurich-Wallisellen, Switzerland, assignor to Machine Tool Works Oerlikon, Administration Company, Zurich-Oerlikon, Switzerland Filed Dec. 12, 1960, Ser. No. 75,181 Claims priority, application Switzerland Dec. 16, 1959 1 Claim. (Cl. 101336) This invention relates to ribbon reversing mechanisms for type impression machines, such as calculating machines.

In particular, this invention relates to ribbon reversing mechanisms wherein two ribbon spools and the respective worm wheels, which are drivingly connected thereto and each of which forms part of the worm gear assembly associated with the respective spool, are arranged on a holder, while the worms of the two gear assemblies are seated on a common driving shaft capable of pivoting relatively to the holder, and wherein the pivoting of the holder and the driving shaft relatively to each other is effected by the increased ribbon pull arising at the end of the unreeling stage of either of the spools.

It is a first object of this invention to prevent any undue increase in the ribbon pull at the end of the unreeling stage of one of the spools and thus to eliminate the danger of the ribbon being torn in the body or torn loose from the spools. I

An embodiment of this invention is described with reference to printing calculating machines and illustrated in the accompanying drawing, in which:

FIG. 1 is a top view of the driving assembly; and

FIG. 2 is a cross-section along the line II -II in FIG. 1.

Referring now to the drawing, the worm shaft '5 which is rotatably and axially slidably mounted between the side walls 6 of the machine carries at its ends outside said side walls the Worms 7 and 8. The shaft is driven in a manner not here described in detail by the gear wheel .9

fixed to it and is set in continuous rotation during the operation of the machine.

The worm wheels 10 and 11 are rotatably mounted on bolts 12 positioned at the outer ends of the ribbon spool holder 13. Said worm wheels are designed to mesh alternately with the worms 7 and 8, whose threads are such that the respective driving directions of the worm wheels are opposed when the worm shaft 5 rotates in one direction. To ensure this alternate meshing, the holder 13 is pivoted at a point 32 irnmovably fixed to the framework. Said holder is also provided with guide slots 28 engaged by bolts 29 fixed to the side walls 6. Said holder is capable of pivoting through a small angle in its plane, thus permitting either of the gearings 7, 10 and 8, 11 to become meshed.

The ribbon spools 15 and 16 mounted on the bolts 12 are drivingly connected to the worm wheels 10, 11. The ribbon 14 is guided at a short distance past the printing types 18 by means of pins 17 fixed to extensions of the holder 13. The worm shaft 5 is capable of sliding axially over a short distance. One of its endpositions, the upper one in FIG. 1, is determined by the control part 19 coming up against the upper side wall 6, as drawn in FIG. 1, while the other end-position, the lower one in FIG. 1, is similary determined by the gear wheel 9 coming up against the other, lower side wall 6. To ensure that the worm shaft 5 can only occupy one of said end-positions at a time, the control part 19 presents adouble cone which is engaged by a lever 21 provided with a knife-edge 20. Said lever 21 is pivoted on a bolt 22 fixed to the framework, and its knife-edge is pressed against the double cone of the control part 19 by the compression spring 23. A cam 24 is connected to the control part 19, and a cam FIICCM 25 is connected to the gear wheel 9, both cams having the form of eccentric disks. With the shaft 5 in its lower endposition, a stop 26 connected to the holder 13 comes within the sweep of the cam 24, while, with the shaft 5 in its upper end-position, a similar stop 27 also connected to the holder 13 comes within the sweep of the cam 25. The relative distances and movements between shaft 5 and holder 13 are such that only one of the cams 24, 25 can engage one of the stops 26, 27 at a time, and that the knife-edge 20 of the lever 21 must first run across the contact surface of the cones on part 19 before any of the cams 2'4, 25 can reverse the holder 13. This arrangement ensures perfect dependability in the reversing of the ribbon.

To lock the worm wheel engagement, the holder 13 can be provided with a detention device operating by means of a ball or a detention lever. It is suificient, however, if the disks 31 carried by the guide bolts 29 are designed as spring disks capable of braking the holder 13 at the side walls 6 when said holder pivots.

Assuming the gearing 7, 10 is in mesh. Then the ribbon 14 moves in the direction of arrow A and the ribbon spool 16 unreels. Once the ribbon is completely unreeled from the spool 16, this can no longer rotate, as one of the ribbon ends is fastened to it. As a result, the pull acting on the ribbon increases sharply, preventing the worm wheel 10 from continuing its rotation. But as the worm shaft 5 continues to be driven, it moves upwards (FIG.

1) in axial direction by screwing in mesh with the stationary worm wheel 10, in opposition to the spring 23 pressing the lever 21 against the upper cone surface of the control part 19. With the shaft 5 overcoming this spring pressure, the knife-edge of the lever 21 first moves on to the contact circle of the two cone surfaces-a distance corresponding to half the shifting distance of the shaft 5. From that moment, the axial shifting distance is quickly completed as the knife-edge 20 slides down the lower cone surface of the part 19 and the shaft 5 continues to screw itself along in mesh with the worm wheel 10, so that the shaft 5 reaches its upper end-position. In the course of this shift, the cam 25 comes within the range of the stop 27 and, in the course of further rotation of the shaft 5, knocks up against said stop. As a result, the holder 13 is pivoted anticlockwise, so that the worm wheel 11 meshes with the worm 8 while concurrently the worm wheel gearing 7, 10 becomes disengaged. This marks the compietion of the reversal of the ribbon motion, and the ribbon now runs in the direction of arrow B.

It is of course also possible to reverse the system of engagement between the worm shaft and the worm wheels on the holder 13, to such effect that the ribbon carrier is immovably fixed and the worm shaft is capable of pivoting in addition to its axial slidability.

Having thus described my invention, I claim:

In a ribbon reversing mechanism for type impression machines, a framework, a holder pivotally mounted on said framework, a ribbon with two ends, two spools rotatably mounted on said holder to provide for a reelingup motion of the ribbon on to the one spool and an unreeling motion of the ribbon from the other spool, said ends of the ribbon being connected to the two spools to have one spool stopped by the ribbon at the end of the unreeling of the ribbon from the other spool, two worm wheels carried by said holder, each worm wheel being drivingly connected to one of said spools, a driving shaft supported by said framework for rotation about the axis of said shaft and for axial movement back and forth between two working positions, two worms connected to said driving shaft to drive said worm wheels in opposite directions during the said reeling-up motion and to generate an axial screwing motion of said driving shaft on completion of said unreeling motion, spring-loaded detention means to yieldingly hold the driving shaft in one of said working positions, rocking means to pivot the holder back and forth between two end-positions, in each of which one of said worm wheels meshes with one of said worms, said rocking means comprising cam means connected to said driving shaft and further comprising two followers for said cam means fixed to said holder, in each 4- of said working positions of said driving shaft one of said followers coming within the range od said cam means, to pivot upon rotation of said driving shaft by said rocking means said holder into either one of said two end-posi- 5 tions.

No references cited. 

